1. Field of the Invention
The present invention relates to a data transfer system, a wireless communication device, a wireless communication method, and a computer program that each allow high-capacity data to be transmitted between information apparatuses at a high speed in a short period. The invention particularly relates to a data transfer system, a wireless communication device, a wireless communication method, and a computer program that each allow consumer apparatuses very close to each other to mutually transmit high-capacity data such as image data and music data by wireless at a high speed.
More specifically, the invention relates to a data transfer system, a wireless communication device, a wireless communication method, and a computer program that each allow construction of a device area network for implementing high-quality data transmission that employs UWB communication and has a high transmission rate and a low error rate. The invention particularly relates to a data transfer system, a wireless communication device, a wireless communication method, and a computer program that each allow high-transmission-rate and high-quality data transmission in a device area network employing the UWB communication, with avoiding deterioration of the signal quality in the wireless section associated with an increase in the distance between the apparatuses.
2. Description of Related Art
In recent years, a wireless communication system called ultra wideband (UWB) communication, which employs a very wide frequency band of 3.1 to 10.6 GHz, has been attracting attention. The UWB communication, which is contemplated to be used for a PAN (Personal Area Network) in which the communication distance is about 10 m, has a transmission speed of about 100 Mbps, and the practical use thereof as a wireless communication system realizing short-range ultra-high-speed transmission is expected (refer to e.g. Nikkei Electronics Issue No. Mar. 11, 2002. “Ubugoe wo ageru musen no kakumeiji Ultra Wideband” p. 55 to 66).
For example, in IEEE 802.15.3 and so forth, transmission system for data with a packet structure including a preamble is devised as an access control system in the UWB communication. Furthermore, Intel Corporation (U.S.) contemplates, as an application of the UWB communication, a wireless version of USB (Universal Serial Bus), which is prevalent as a general-purpose interface for personal computers.
The UWB communication is a wireless communication system for short-range communication because of its regulated low transmission power, but allows high-speed wireless transmission. Therefore, as a consumer-use system, the UWB communication can couple, by wireless, mobile digital apparatuses such as digital cameras and music reproduction apparatuses to televisions and personal computers with short distances therebetween, and permits high-speed data transmission of music content and image content therebetween.
In the past, in order to transfer image and music data between plural information apparatuses, typically the apparatuses are interconnected via a general-purpose cable such as an AV cable or USB cable for the data communication, or a medium such as a memory card is physically moved between the apparatuses. In contrast, if data transfer between apparatuses employing wireless interfaces is allowed, there is no need to change the connectors and route a cable every data transmission, which offers high convenience. In recent years, mobile apparatuses that are provided with a wireless communication function for the purpose of exchanges of image and music data with a personal computer have also emerged (refer to e.g. http://pcweb.mycom.co.jp/news/2002/09/03/10.html).
If the above-described UWB communication system is used for the wireless data exchange between apparatuses, wireless transmission of high-capacity data at a transmission rate of about 10 Mbps can be realized although the allowable communication distance is short. Alternatively, it is also possible to apply infrared communication or an IEEE802 wireless LAN system of course. However, since the UWB communication is a short-range and high-capacity wireless communication system, high-speed data transmission in an ultra-short-distance area, such as an ultra-high-speed and short-range DAN (Device Area Network) including a storage device, can be realized by the UWB communication. For example, the UWB communication allows high-capacity data such as moving image data and music data corresponding to music in one CD to be transferred at a high speed in a short period.
Transmission systems employing a UWB low band of 3.1 to 4.9 GHz are also being intensively developed because of advantages thereof that data transmission over 100 Mbps is possible without occupying the transmission band of 3.1 to 10.6 GHz, and that an RF circuit can be fabricated easily. The present inventor is considering the data transmission system utilizing the UWB low band as one of effective wireless communication techniques incorporated into mobile apparatuses.
However, communication by use of wireless signals involves a problem in that the signal quality in the wireless section is deteriorated in association with influence of peripheral reflectors and an increase in the distance between the apparatuses carrying out the communication. In particular, this signal quality deterioration makes it difficult to implement high-transmission-rate communication and high-quality transmission with a low error rate.